Prediction And Comprehensive Optimization Of Vehicle Aerodynamic Sound Quality Based On Occupant Perception

Wind noise is an important indicator of comfort when the car is running at high speed,and wind noise simulation optimization is a necessary tool in the pre-development stage.Due to the complex wind noise propagation process,a lot of wind noise optimization work has been carried out in the past based on the simulation of window pressure pulsation,while the hydrodynamic pressure of the side window pressure pulsation,which accounts for the main energy contribution,is much lower than the acoustic pressure,resulting in the average pressure pulsation of the window is difficult to reflect the correct trend of wind noise perception of the human ear of the vehicle occupants.And due to the influence of human ear structure and psychoacoustics,the overall sound pressure level alone cannot reflect the real feeling of occupants' human ears and is difficult to apply to wind noise optimization.Therefore,it is important to study the wind noise quality prediction and optimization method based on the human ear wind noise perception in wind noise environment.Firstly,an accurate and efficient numerical simulation method is built based on wave number decomposition and statistical energy analysis for the prediction of the wind noise response of the occupant's ear in the vehicle.Secondly,psychoacoustic evaluation indexes such as loudness,sharpness and speech intelligibility are introduced to propose an objective evaluation method of sound quality reflecting occupant's human ear perception under wind noise environment.Then the wind tunnel test and numerical simulation are combined to analyze the change law of wind noise quality inside the car under different shapes and window opening conditions.Finally,the wind noise control method is explored from three aspects of leakage,shape and buffeting noise to optimize the interior sound quality.It provides new ideas and methods for the development of vehicle wind noise,which has important theoretical significance and engineering application value.The main contents are as follows.(1)For the side window pressure pulsation load calculation,firstly,through the wind tunnel static pressure test verification and different simplified car model flow field,acoustic field simulation comparison analysis,in different wind speed and yaw conditions,realizable k-? can accurately simulate the time-averaged flow field around the vehicle.Secondly,the accuracy of the side window pressure pulsation simulation of the three turbulence models was verified by comparing the aeroacoustic wind tunnel test.The high frequency pressure level of the improved detached vortex simulation(IDDES)is significantly lower than the test,while the high frequency wind noise pressure level of the large vortex simulation(LES)decays more slowly and is closer to the test spectrum trend.The LES with higher accuracy is selected for the side window pressure pulsation calculation to provide accurate load input for the in-vehicle wind noise response calculation.(2)The wave number decomposition(WND)theory is introduced,and the direct noise calculation(DNC)and statistical energy analysis(SEA)are combined to propose an in-vehicle occupant human ear wind noise response calculation method.The simulation method accurately predicts the wind noise trend in different shapes of the car after comparing and verifying different simplified car models in wind tunnel tests.In contrast to the traditional method,this method simultaneously considers the energy level magnitude of sound pressure and hydrodynamic pressure in the window pressure pulsation and the window transmission efficiency by wave number analysis,etc.,which improves the simulation accuracy.And in the high frequency band where the sound quality index is widely concerned,the modal density is high,and the use of SEA has the advantage of high computational efficiency.It provides the basis of simulation method for the prediction of wind noise quality in the early stage of vehicle development.(3)Combined with the human ear structure,we analyzed the hearing characteristics of occupants,introduced psychoacoustic evaluation indexes such as loudness,sharpness and speech intelligibility,and proposed an objective evaluation method for in-vehicle wind noise quality that can reflect the perception of the human ear of occupants.Wind tunnel tests are conducted on five simplified car models under different working conditions,and the change law of interior sound quality under different wind speeds and yaw angles is analyzed based on artificial heads,and the shape wind noise characteristics are analyzed in combination with windows and far-field wind noise to provide reference for interior sound quality optimization.(4)For the open window condition,firstly,a buffeting noise simulation model based on the compressible LES turbulence model is established,and the mechanism of pressure change in the passenger cabin during shear vortex shedding is analyzed.Secondly,based on the customized broadband sound source function,a cabin frequency response simulation method is established to analyze the Helmholtz resonance characteristics of the cabin when the window is open.Finally,based on the human ear perception of the occupants,the wind tunnel test is conducted to investigate the buffeting characteristics and sound quality changes under different wind speeds,window openings and window combinations,so as to summarize the law for the optimization of sound quality when opening windows.(5)Combined with wind tunnel test and numerical simulation,the three aspects of wind noise control methods are investigated from leakage noise,shape noise and buffeting noise.1)For the leakage noise,firstly,the wind noise characteristics of the real car are investigated based on the wind tunnel test,and secondly,the contribution of the speech intelligibility of the local leakage of the body is investigated based on the window opening method,and the leakage control is carried out from the body and the rear view mirror seal,etc.2)For shape noise,firstly,multi-region wave number analysis is proposed to improve the simulation accuracy of wind noise inside the real car.Secondly,the shape noise control method is explored through rearview mirror reshaping and body insulation.3)For buffeting noise,firstly,the spoiler and separator bar passive control method is proposed,and the best shape is obtained through parameter optimization.Secondly,the active control method of B-pillar jet and anti-phase sound source method is proposed to effectively suppress the buffeting noise without changing the body shape.Finally,the active control method based on control logic combined with opening adjustment,combined window opening and inverse phase sound source method is proposed to effectively suppress the buffeting of side windows without affecting the occupant's view and less energy output to improve the interior sound quality.This paper integrates direct noise calculation,wave number decomposition and statistical energy analysis,and introduces psychoacoustic evaluation indexes to propose a numerical calculation method of sound quality that can reflect the human ear perception of occupants in wind-noise environment.Combined with wind tunnel tests and numerical simulations,the mechanism of wind noise formation and the law of sound quality change are analyzed and summarized,and the optimization of interior sound quality is explored from multiple wind noise sources.It provides new ideas and methods for vehicle wind noise development.